Process and apparatus for loading dies for forming ceramic tiles

ABSTRACT

In the process and apparatus of the invention, a layer of powders bearing patterns is laid on a rest surface of a belt conveyor, the conveyor belt is introduced between the bottom die and the top die above a cell afforded in the bottom die, the layer of powders is unloaded into the cell by a swift withdrawal of the belt conveyor. The withdrawal of the unloading end of the conveyor belt is carried out with no relative dragging between the rest surface and the bottom of the layer of powders, by means of a translation which is parallel to the rest surface and which is very rapid.

BACKGROUND OF THE INVENTION

[0001] Specifically, though not exclusively, the invention isparticularly applicable in the field of loading devices structured forarranging internally of the forming cells of the die, and generallyabove a previously-laid layer (constituted by larger-grain supportmaterial), a further layer of powder material, generally finer and ofbetter quality, which is destined to form the decorated surface of thetile which will be in view.

[0002] Devices of this type are known, generally referred-to asdouble-loading devices, and combine with a usual press-loading tray ortruck various devices, among which small conveyor belts which, workingin synchrony with the tray or truck, carry out the above-mentioneddouble-loading operation by depositing a further layer of powder in thecell, previously-filled from the tray.

[0003] The main limitation in the prior art consists in the considerabledeformation which the decoration (in powder-form) is subject to when itis dropped from the end of the conveyor belt during the latter'shorizontal passing movement over the forming cell.

[0004] In effect this passing movement creates a sort of “waterfall”effect, causing an undesired remixing of the powders which is furtheraccentuated by the impact of the falling powders (the second load) onthe underlying powders already deposited on the bottom of the cell fromthe first loading operation. The desired kinematic solution should bethat the displacement speed (retreat) of the conveyor belt is equal andopposite to the transport speed of the belt on which the powders aredeposited. This condition, however, is increasingly more difficult tomaintain as the speeds increase.

[0005] A further drawback in the prior art is that the unloading timesare quite considerable and add to work-cycle times.

[0006] The main aim of the present invention is to obviate the abovedrawbacks in the prior art by providing a process for depositing thepowders which does not alter in any significant way the structure of thelayer that is deposited.

[0007] An advantage of the invention consists in its being applicable toany existing type of ceramic press.

[0008] A further advantage of the invention is that it enables a trueand proper decoration line to be set up, directly applied on the upperbranch of the conveyor belt and composed of a plurality of decoratordevices which can therefore produce different decorations. The number ofpossible decorations, however, does not in any way influence the workcycle time.

[0009] These aims and advantages and more besides are all attained bythe present invention, as it is characterised in the appended claims.

SUMMARY OF THE INVENTION

[0010] The invention relates to a process for loading dies for formingceramic tiles, of a type where a layer of powders bearing a decorationis laid on a rest surface of a conveyor belt, the conveyor belt isintroduced between a bottom die and a top die above a cell afforded inthe bottom die, and the layer of powders is dropped into the cell as theconveyor belt is retreated; characterised in that at least a retractionof the unloading end of the belt conveyor occurs without any relativedragging between the rest surface and a bottom of the layer by means ofa translation of the unloading end, which is parallel to the restsurface and which retraction is characterised by being very rapidlyexecuted.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Further characteristics and advantages of the present inventionwill better emerge from the detailed description that follows of apreferred but nonexclusive embodiment of the invention, illustratedpurely by way of a nonlimiting example in the accompanying figure, inwhich:

[0012]FIG. 1 is a schematic side view in vertical elevation;

[0013]FIGS. 2, 3 and 4 are the same view as FIG. 1 in three differentoperating configurations;

[0014]FIG. 5 is a schematic view of the detail of the belt removed fromthe rest of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] With reference to the figures, 1 schematically denotes a pressfor forming ceramic tiles, with a bottom die 2, affording a cell 4destined to receive the powders to be pressed, and a top die 3.

[0016] A usual tray 5 is positioned in a raised position between thebottom die 2 and the top die 3, which tray 5 has the task of depositinga first layer of powder material in the cell 4; this powder willfunction as a “support” for a second layer, generally composed ofbetter-quality and finer material and laid in a thinner layer, whichwill form the final in-view decorated surface of the tile. The secondlayer is loaded into the cell 4 on top of the bottom layer, previouslyloaded by the tray 5, by the device of the invention, specially made foreffecting this second loading operation.

[0017] The process for effecting this second loading operation involvescreating a layer of powders 8 having decorations on the rest surface ofa belt conveyor 7, the introduction of the belt conveyor 7 between thebottom die 2 and the top die 3 above the cell 4 afforded in the bottomdie 2, followed by the unloading of this layer 8 into the cell 4contemporaneously with the retreat of the belt conveyor 7. The inventionis distinguished from the prior art by the fact that at least theretreat of the unloading end of the belt conveyor 7 occurs, with norelative dragging between the rest surface and the base of the layer 8,through a translation of the unloading end which is parallel to the restsurface and which is characterised by a high-speed execution, so as toremove the rest surface from beneath the layer 8 of powders veryswiftly, causing the powders to fall vertically with no friction againstthe unloading end. In effect, the unloading end retreats so quickly thatthe powders forming the layer 8, having their support removed frombeneath them, fall freely and vertically.

[0018] During the unloading stage, evidenced in FIG. 3, the drawingdevice 17 remains inactive while the slide 13, and with it the unloadingend of the belt conveyor 7, are retreated very quickly by the drawingpulley 27 which pulls the conveyor belt 23. It is at this stage that thevarious decorations at the various decorating stations are unloaded fromthe dry decoration dispensers 25.

[0019] The perfect adherence of the belt 11 to the head 12 is ensured bya stretcher 16 pulling constantly in the direction indicated by thearrow.

[0020] The layer 8 is composed of a bottom part 9 on which a topdecorative layer 10 is deposited, comprising powders arranged accordingto predetermined patterns.

[0021] With the process of the invention, the layer of powders isdropped in such a way that the structure of the layers deposited is notchanged, especially the part thereof which forms the pattern of thedecoration.

[0022] The various points of the layer 8 have parallel and uniform droptrajectories which enable the structure of the decorations present onthe top decorative layer 10 to remain unaltered. Further, the bottompart 9 functions somewhat as a buffer, softening the impact with thefirst layer of material already present on the bottom of the cell 4 andpreventing a further re-mixing of the powders in the top decorativelayer 10.

[0023] The above-described process is carried out by an apparatus forloading dies for ceramic tile-forming, which comprises at least one beltconveyor 7, a terminal part of which, known as the unloading end, atwhich the belt 11 of the belt conveyor 7 winds about a head 12, andreturning at an angle of about 180°, is constrained to a slide 13 whichcan be commanded to translate in two senses along a guide 24 in aparallel direction to the rest surface of the belt conveyor 7.

[0024] The belt 11 is ring-wound and has an upper branch 14 on which thepowders rest and a lower branch 15, parallel to the upper branch 14; thebelt 11 is also associated to a stretcher 16 which keeps the belt 11 inconstant tension.

[0025] A drawing device 17 is also associated to the belt 11 and oncommand controls the motion of the upper branch 14 of the belt 11.

[0026] The belt 11 is wound on a series of snub pulleys whicheffectively give rise to a doubled upper branch, denoted by 18 in FIG.5, parallel and moving in the same direction as the upper branch 14, anda doubled lower return branch 19 which is parallel to the doubled upperbranch 18 and is generated by the 180° return of the belt about a headpulley 20.

[0027] The head pulley 20 is mounted idle on a cursor 21 which is guidedto slide freely along a guide 22 in a parallel direction to the slide 13movement direction.

[0028] The cursor 21 and the slide 13 are reciprocally constrained todisplace to the same degree, in the same direction, but in oppositesenses. A drawing pulley 27 is associated to the cursor 21 and the slide13 and on command causes both to slide.

[0029] The cursor 21 and the slide 13 are indeed reciprocally connectedby a belt 23 ring-wound about a system of fixed pulleys.

[0030] The illustrated apparatus enables the unloading end of the beltconveyor 7 to be introduced and retreated into and out of the spacecomprised between the bottom die 2 and the top die 3.

[0031] Furthermore, the possibility of keeping the upper branch 14 ofthe belt 11 still during the retreat phase, and of moving the belt 11and the unloading end during the introduction step, as well as thespecial configuration of the belt conveyor 7, enable the problem-freesetting-up of a true and proper decorating line, containing severaldry-decoration dispensers 25, which are therefore able to producevarious decorations directly using the upper branch 14 of the beltconveyor 7. During the introduction step of the process, shown in FIG.2, the machine for applying the bottom 26 of the powders destined toconstitute the part of the bottom part 9 of the layer 8 is brought intoaction; this machine is located upstream of the dry-decorationdispensers 25, so that the bottom part 9 can be deposited first.

[0032] During the introduction step, illustrated in FIG. 2, the drawingpulley 27 is activated to advance the slide 13, with a consequentretreat of the cursor 21. The drawing device 17 draws the belt 11 sothat the upper branch 14 advances at the same speed and in synchronywith the unloading end of the belt conveyor 7, and the pulley 28 drawingthe small belt of the machine for applying the bottom 26 draws the smallbelt in synchrony with the belt 11 so that it can deposit the bottompart 9 of the layer 8.

What is claimed: 1). A process for loading dies for forming ceramictiles, of a type where a layer of powders bearing a decoration is laidon a rest surface of a conveyor belt, the conveyor belt is introducedbetween a bottom die and a top die above a cell afforded in the bottomdie, and the layer of powders is dropped into the cell as the conveyorbelt is retreated; wherein at least a retraction of the unloading end ofthe belt conveyor occurs without any relative dragging between the restsurface and a bottom of the layer by means of a translation of theunloading end which unloading end is parallel to the rest surface andwhich retraction is characterised by being very rapidly executed. 2).The process of claim 1, wherein the translation of the unloading endoccurs with no forward movement of the rest surface. 3). The process ofclaim 1, wherein the retreating translation of the unloading end occursat a speed which is such as to cause the powders forming the layer tofree-fall with no dragging against the unloading end. 4). The process ofany one of the preceding claims, wherein the layer is composed of abottom on which an upper decorative layer is laid, which upperdecorative layer comprises powders laid according to predeterminedpatterns. 5). An apparatus for loading dies for ceramic tile-forming,wherein it comprises a belt conveyor having an unloading end portion atwhich a belt of the belt conveyor winds about a head and turns about toan angle of about 180°; the head being able to translate on command intwo senses in a direction which is parallel to a rest surface of thebelt conveyor; the belt being closed and ring-wound in such a way as todefine an upper branch for the powders and a returning lower branch,parallel to the upper branch and being associated to a stretcher whichkeeps the belt in a state of tension; a first drawing device beingassociated to the belt, which first drawing device can be commanded tocontrol operation of the upper branch. 6). The apparatus of claim 5,wherein the head is constrained to a slide which can be commanded by asecond drawing device to translate in two senses according to thetranslation direction. 7). The apparatus of claim 6, wherein the belt iswound about a series of snub pulleys which together define a doubledupper branch, comprising the upper branch and the lower branch, with thelower branch parallel to the upper branch, and a returning doubled lowerbranch which is parallel to the doubled upper branch and is generated bya 180° deviation of the belt about a head pulley; the head pulley beingmounted idle on a cursor which is guided to slide freely along a guidein a parallel direction to a motion direction of the slide; the cursorand the slide being reciprocally constrained to make displacements of asame entity, in a same direction, but in opposite senses. 8). Theapparatus of claim 7, wherein the cursor and the slide are reciprocallyconnected by a third conveyor belt ring-wound about pulleys.